3rd generation partnership project (3GPP) long term evolution (LTE) evolved from a universal mobile telecommunications system (UMTS) is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas.
In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) evolved from the 3GPP LTE. The 3GPP LTE-A ensures backward compatibility with the 3GPP LTE, and supports a wideband by using carrier aggregation.
The 3GPP LTE system supports only one bandwidth (i.e., one component carrier) among {1.4, 3, 5, 10, 15, 20}MHz. In order to support a full bandwidth of 40 MHz, carrier aggregation uses two carriers having a bandwidth of 20 MHz or uses 3 carriers respectively having bandwidths of 20 MHz, 15 MHz, and 5 MHz. One component carrier corresponds to one cell.
The carrier aggregation can support backward compatibility with legacy systems, and can significantly increase a data rate by using a plurality of component carriers.
In a single-carrier system, a control channel and a data channel are designed on the basis of a single component carrier. However, it may be ineffective if the channel structure of the single-carrier system is directly used in the multi-carrier system.
In particular, in 3GPP LTE, the control channel is monitored only in a specific region of a subframe. Since a plurality of component carriers are used due to carrier aggregation, there is an increase in an amount of control information for the plurality of component carriers. Therefore, it may be not enough to transmit all control channels by using only a region for the conventional control channel.